There is a critical shortage of donor organs. Hundreds of lives could be saved each day if more organs (heart, kidney, lung, etc.) were available for transplant. While the shortage is partly due to a lack of donors, there is a need for better methods of preserving and transporting donated organs. Current storage and preservation methods allow only a small time window between harvest and transplant, typically on the order of hours. These time windows dictate who is eligible to donate organs and who is eligible to receive the donated organs. These time windows also result in eligible organs going unused because they cannot be transported to a recipient in time.
The transport window is most acute for heart transplants. Current procedures dictate that hearts cannot be transplanted after four hours of ischemia (lack of blood supply). Because of this time limit, a donor heart cannot be transplanted into a recipient who is located more than 500 miles (800 km) from the harvest. In the United States, this means that a critically-ill patient in Chicago will be denied access to a matching donor heart from New York City. If the geographic range of donors could be extended, thousands of lives would be saved each year.
While several state-of-the-art preservation methods are available to keep organs viable within a hospital, transport preservation typically involves simple hypothermic (less than 10° C.) storage. Contemporary transport storage (i.e. “picnic cooler” storage) typically involves bagging the organ in cold preservation solution and placing the bagged organ in a portable cooler along with ice for the journey. There are no additional nutrients or oxygen provided to the organ. For the most part, the hope is that the preservation solution will reduce swelling and keep the tissues moist, while the cold reduces tissue damage due to hypoxia.
This method of transport has several known shortcomings, however. First, the temperature is not stabilized. Because the temperature of the organ is determined by the rate of melting and the thermal losses of the cooler, an organ will experience a wide range of temperatures during transport. For example, the temperatures can range from nearly 0° C., where the organ risks freezing damage, to 10-15° C., or greater, where the organ experiences greater tissue damage due to hypoxia.
Second, the organ does not receive sufficient oxygen and nutrients. Even though the metabolic rate is greatly slowed by the low temperatures, the tissues still require oxygen and nutrients to be able to function normally once the tissue is warmed. While some nutrients are provided by the preservation fluid surrounding the organ, the nutrients are not readily absorbed by the exterior of the organ due to the presence of a protective covering, e.g., the renal capsule.
Third, there is little protection against mechanical shock. An organ sealed in bag and then placed in a cooler with ice is subject to bruising and abrasion as the organ contacts ice chunks or the sides of the cooler. Mechanical damage can be especially problematic when the organ is airlifted and the aircraft experiences turbulence.
One newer alternative to “picnic cooler” transport is to transport the sample in a container that actively perfuses the sample with a preservation fluid, for example, University of Wisconsin solution. Such systems typically require a battery to power the pump, which means that the overall system is heavier, and limited to the useable lifespan of the battery. Perfusion transport systems also suffer from bubble formation within the perfusate due to constant jostling of the system during transport. In some cases, bubbles formed in the perfusate may be accidentally forced into the capillaries of the sample (e.g., donor heart) causing irreparable harm. An organ that is spoiled because of bubbles may not be identified as damaged until it is transplanted into a donor.
Improved transport and storage for organs would increase the pool of available organs while improving outcomes for recipients.